SDRAM实验怎么会有这种错误？ target, Trouble, operation, during, before

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为什么在SDRAM实验中，程序在运行时，观察变量的值时，弹出这 种错误，暂定程序也不行，同样报错。
Trouble Halting Target CPU: Error 0x00000020/-1141 Error during: Execution, &nbsprocessor communication timeout. It is recommended to RESET EMULATOR. This will disconnect each target,   perform an emulation reset, and then reconnect each target. Power cycle the target board before continuing.   Sequence ID: 15 Error Code: -1141 Error Class: 0x00000020
1 other operation(s) were automatically canceled as a result
大家有遇到这种情况没？是什么原因啊？